使用Nodejs连接mongodb数据库的实现代码

5. 查询所有文档

添加findDocuments函数

var findDocuments = function(db,callback){
  // get the documents collection
  var collection = db.collection('documents');
  // find some documents
  collection.find({}).toArray(function(err,docs){
    assert.equal(err,null);
    console.log("Found the following records");
    console.log(docs);
    callback(docs);
  });
};

findDocuments函数查询了所有’documents’集合中所有的文档，将此函数添加到MongoClient.connect的回调函数中

var MongoClient = require('mongodb').MongoClient
 , assert = require('assert');
// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
 assert.equal(null, err);
 console.log("Connected correctly to server");
 insertDocuments(db, function() {
  findDocuments(db, function() {
   db.close();
  });
 });
});

6. 使用过滤条件(query filter)查询文档

查询’a’:3的文档

var findDocuments = function(db, callback) {
 // Get the documents collection
 var collection = db.collection('documents');
 // Find some documents
 collection.find({'a': 3}).toArray(function(err, docs) {
  assert.equal(err, null);
  console.log("Found the following records");
  console.log(docs);
  callback(docs);
 });
}

7. 更新文档

var updateDocument = function(db,callback){
  // get the documents collection
  var collection = db.collection('documents');
  // update document where a is 2, set b equal to 1
  collection.updateOne({a:2},{
    $set:{b:1}
  },function(err,result){
    assert.equal(err,null);
    assert.equal(1,result.result.n);
    console.log("updated the document with the field a equal to 2");
    callback(result);
  });
};

updateDocument方法更新满足条件a为2的第一个文档，新增一个b属性，并将其设置为1。

将updateDocument方法添加到MongoClient.connect方法的回调中

MongoClient.connect(url,function(err,db){
  assert.equal(null,err);
  console.log("Connection successfully to server");
  insertDocuments(db,function(){
    updateDocument(db,function(){
      db.close();
    });
  });
});

8. 删除文档

var removeDocument = function(db,callback){
  // get the documents collection
  var collection = db.collection('documents');
  // remove some documents
  collection.deleteOne({a:3},function(err,result){								 
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